For Winston Churchill, the same rules apparently applied: #NeverGiveIn.

In a bizarre twist, this phrase now serves as the tagline for former Secretary of Defense Donald Rumsfeld’s inaugural mobile game Churchill Solitaire, which he created in partnership with a team of coders.

Churchill Solitaire is essentially a more challenging version of the traditional card game. In place of a single deck players use two decks, and work with 10 rows of cards rather than the typical seven. Churchill played the game during World War II to sharpen his strategic thinking skills, according to Rumsfeld.

In Rumsfeld’s app, there are varying levels and difficulties as players move up the ranks. Created for the most cunning of minds, a series of rules and limitations make the game especially challenging. For example, if the player doesn’t make a move in 30 seconds, he’s forced to surrender.

The game’s “diabolical rules,” Rumsfeld says, are what “make it the hardest game of solitaire — and probably the most challenging and strategic game of logic or puzzle — I’ve ever played.”

Rumsfeld said he learned the card game from one of the Churchill’s former proteges, André de Staercke, during a plane ride in the 1970s. Staercke had learned the game from Churchill himself.

Until recent years, only a few people knew about the game and even fewer were able to find their way to victory.

Inspired to share the tradition, Rumsfeld and his wife worked with a team of developers to perfect the game. The non-profit endeavor took years to build after the Churchill family gave the project their blessing. All profits will go to charity. However, a free version is available in the Apple Store for both iPhones and iPads.

The motivation for the app, Rumsfeld wrote, was best explained by Staercke himself.

“As my friend Andre de Staercke once put it to me, ‘What one needs in life are the pessimism of intelligence and the optimism of will,’ Rumsfeld wrote. “Play a couple hands of Churchill Solitaire, and you’ll know precisely what he meant.”